Buchi



Feb. 9, 1960 A. BUCHI 2,924,069

TWO-STROKE INTERNAL COMBUSTION ENGINES Filed Feb. 15, 1955 5 Sheets-Sheet 1 A. BUCHI 2,924,069

Feb. 9, 1960 TWO-STROKE INTERNALCOMBUSTION ENGINES 5 Sheets-Sheet 2 Filed Feb. 15, 1955 'Feb. 9, 1960 TWO-STROKE INTERNAL COMBUSTION ENGINES s Sheets-Sheet a Filed Feb. 15. 1955 Feb. 9, 1960 A. BUCHI 2,924,069

TWO-STROKE INTERNAL COMBUSTION ENGINES Filed Feb. 15, 1955 5 Sheets-Sheet 4 Feb. 9, 1960 A. BUCH] 2,924,069

TWO-STROKE INTERNAL COMBUSTION ENGINES Filed Feb. 15, 1955 5 Sheets-Sheet 5 TWO-STROKE INTERNAL COMBUSTION ENGINES Alfred Buchi, Hurden, Switzerland Application February 15, 1955, Serial No. 488,210

Claims priority, application Switzerland February 17, 1954 14 Claims. (CI. 60-13) The present invention relates to two-stroke internal combustion engines with exhaust gas turbo-charging.

Ugimd ta tent- In the engines according to the invention, first of all,

o'f -the working cylinders is effected at .a higher pressure through special inlet ports in said cylinders, with; the exhaust and scavenging air ports closed, the supercharging air being delivered by at least one blower driven by the engine or otherwise. Thus there is provided according to the invention two-stroke internal combustionengines comprising a plurality of working cylinders, each having at least one exhaust port, at least one port for the admission of scavenging air, and at least one port for the admission of supercharging air, at least one turbo- -blower driven solely by the exhaust gases of the engine,

means connecting the output of said turbo-blower to said scavenging air ports, and' means for delivering supercharging air to said supercharging air ports at a higher pressure than said scavenging air, while the scavenging air ports and exhaust ports are closed. Advantageously, the device for the delivery of'the supercharging air (the supercharger) driven by the engine or otherwise, is dimensioned for. such a large eifective delivery that the supercharger delivers the theoretical air requirement for the quantity of fuel necessary for starting and accelerating the engine to its working speed.

Furthermore, the inlet ports for the supercharging air may be directed tangentially into the working cylinders so that, during the supercharging process, a rotary movement of the cylinder contents is produced in such a manner that the inner cylinder wall is additionally cooled and/ or thedistribution and atomisation of the fuel introduced is improved. At least one closure member may be exhaust gas ports in the: cylinders, thelclosure member being closed during the time the supercharging ports are kept open in the cylinders, and is held open during the exhaust and scavenging process, and atleast one further provided, in each-of the exhaust gas ducts, beyond the I closure member maybe provided between the supercharging ports in the cylinders and the supercharger, which member is so controlled that, during the actual exhaust and scavenging period, the delivery duct between the supercharger and its inlet ports into the cylinder the supercharger obtains its delivery .air from the scavenging air distributorof the engine.

The exhaust gas turbo-blower may in known manner receive the exhaust gases of the engine through separate v The delivery .air. of the blowendriven -by the exhaust 2 gas turbine, as well as that from the device delivering remains closed. The construction may also .be such that 'enging and supercharging air,

I 2,924,069 Patented Feb, 9, 1

supercharging air, or only one of these quantities of air, may be cooled.

The drive of the supercharger device may be so formed that by means thereof the supercharging air delivered-t6 the engine is variable in quantityor pressure or both. .The inlet ports in the cylinder for the supercharging air may be offset longitudinally of the cylinder relatively .to the corresponding ports for theinlet of the scavenging air, whereby to facilitate the passage of the piston rings over saidports. i

In the duct conveying supercharging air to the cylinders, it is possible to provide a blow-cit member, which delivers its blow-off air to the scavenging air distributor of the engine. The drive for the closure members for the exhaust gas and that for the supercharging air may be derived from the engine crankshaft or cam-shaft. The drive of the supercharging air pump may also be effected off one or other of said shafts by means of a separate or the same device. j It is therefore an object of the present invention to provide a two-stroke cycle internal combustion engine providing complete scavenging and 'positiVe'supercharg ing.

It is a further object of the present invention to pro vide a more efficient two-stroke cycle internal combustion engine by appropriat'e location and control of exhaust, scavenging air, and supercharging air ports in the cylinders of the engine.

Other and further objects and advantages will become apparent from the following specification taken with the accompanying drawings in which like characters of ref erence designate similar parts in the several views, and in which: I

Figure 1 shows a vertical section through a two-stroke engine, in which the exhaust gases leave the engine through a closure member in the cylinder 'cover, and ports are arranged in the cylinder for the inlet of scav- Figure 2 shows a special arrangement of the supercharging ports in a horizontal section on the line 1-1 inFigure 1, I i

Figure 3 shows the supercharger in elevation,

Figure 4 on the other hand represents a two-stroke engine, likewise in vertical section, in which the exhaust gas ports as well as the scavenging air and supercharg ing air ports are arranged in the cylinder wall,

Figure 4a is a fragmental sectional view illustrating'the connection between the receiver and the scavenging air ports,

Figure 5 represents a vertical section through a, twostroke internal combustion engine equipped with-opposed pistons,

' Figure 6 represents a vertical section through a cylinder of a two-stroke engine, in which the scavengingand super;- charging air enterthrough: ports into the cylinder, and the'exhaust' gases likewise escape through;ports in the cylinder tothe'turbine of the exhaust gas turbo-blower,

a double-acting pistonpump being provided as a supercharging pump, and

Figure: 7 shows the pressure variation in a cylinderof a two-stro'keengine operating'inaccordance with the invention, as well as the corresponding control times of the various'inlet andoutlet members," and also the special closure members 'for'the exhaust gases and superchargsa -w In Figure l, l'is the engine frame, in which is mounted a cylinder 2, both of which are closed at the top bya cylinder head 3. 4 is the working piston of .the engine. 5 is an exhaus t gas =turbine, which drives the, blower 6 mechanically,. independently 'of,tlie'..-eugihev The x} haustv gases. from I the engine pass through the fqutle't 7 and the duct "8 to the tuibine'S addflienceoht again;

- 3 through the pipe 9. The scavenging air is drawn in at by the blower 6 and delivered through the pipe 11 to the scavenging air distributor or receiver 12 of the engine. Thence it passes through the scavenging air ports 1'3 to the cylinder chamber 14 of the engine. According to the invention, there are now provided in the cylinder wall ports 15 above the ports 13; said ports 15 serve for the introduction of the supercharging air. This supercharging air is taken from the scavenging air distributor or receiver 12 and passes through the duct 16 (in reversible engines generally through a reversing member 17) into the Roots" blower 18 and is thence delivered through the duct 19 to the closure member 20, which during the appropriate period, allows the superchar'ging air to enterthe supercharging ports 15. Mounted in the duct 19 there is also a cooler 21, by means of which the supercharging air is cooled before entering the cylmder The cooling water enters through the pipeline 22 and leaves again through the pipeline 23. The mechanical drive of the Roots blower 18 is elfected as shown in Figure 3 by the chain 24, which is driven off the crankshaft 25 (Figure 1) by means of the sprocket 2 6. 30 is the cam shaft of the engine; this is driven by the chain 31, which is likewise driven oif the crankshaft 25 by the sprocket 32. The chain 31 also drives the closure member or valve by means of the wheel 33. Said valve 20 and the cam shaft 30 are driven by a single endless chain 31 which passes over the two guide rollers 34 and 35. The exhaust valve 36 is actuated in known manner off the cam shaft 30 by means of the rod gear 37. In accordance with the position of the piston 4- and the cam shaft 30 of the engine, shown in Figure l, exhaust of the exhaust gases is taking place through the outlet 7 and the open exhaust valve 36 into the turbine 5. At the-same time, scavenging air from the scavenging air container 12 enters the cylinder through the ports 13. At the same moment of the working cycle, however, the member 20 is closed towards the supercharger 18 and at that moment, no supercharging air can enter the cylinder 14 through the ports 15. When now the engine rotates further in the direction of the arrow A, the scavenging ports 13 are closed by the piston 4, the exhaust valve 36 also closes and the passage of supercharging air through the ports 15 to the cylinder 14 is released by rotation of the valve 20, so that this air can enter the cylinder without interference, either by the exhaust or the scavenging process and the cylinder can be filled with a highly compressed charge.

As seen in Figure 2, the supercharging ports 15 preferably have a tangential direction of inlet relatively to the cylinder 14. Since in addition, as will be seen in Figure 1, said ports are directed obliquely upward in the cylinder, the incoming supercharging air will assume a rotary motion towards the upper part of the cylinder space, and at the same time will reach the walls of the cylinder 14 and in addition cool them. The fuel entering through the fuel valve 40 is distributed and atomised still better by this whirling of the air.

Figure 3 shows a side view of the supercharger 18 i with its supply pipe 16 and its delivery pipe. In the illustrated embodiment, the supercharger 18 is driven by a speed change gear 60. By adjustment of the lever 61 on the supercharger 18, the latter may be given different speeds. This gear 60 is driven by the chain 24.

Referring now to Figure 4 there is illustrated a twostroke engine in which both the exhaust gas ports aswell as the scavenging air and supercharging air ports are arranged in the cylinder wall. are indicated by the reference 7a in this case and the scavenging air ports and supercharging air ports are indicated respectively by 13a and 15a. It will be noted that'in this embodiment, there being no cam shaft, the chain31 drives instead the rotary closure member 36a in the exhaust pipe 8. The supercharger 18 is then driven by chain 24a from wheel 26a mounted on an extension of the shaft of the closure member 20.

The exhaust gas ports through the valve 40a.

In the supply line 19 for the supercharging air a blowofi or safety valve 77 is provided which opens into the scavenging air receiver 12. During the period line 19 is closed by the member 20 supercharging air may be added thereby to the scavenging air supply.

A feature of the embodiment according to Figure 4 is the provision of cooler 21 which corresponds to cooler 21 of Figure l and is provided in the pressure line 11 from the turbo-blower to the distributor 12, the cooling medium entering at 22' and leaving at 23'. I

Figure 4 shows the position of the piston shortly after the lower dead centre. During this period, scavenging of the cylinder takes place through the open scavenging air ports 13a and the swept-out cylinder contents pass through the outlet ports 7a and the exhaust gas pipe 8 to the turbine 5 and, after they have done work, to the exhaust pipe 9. At the same moment, the supercharging ports are also uncovered by the piston. Since member 20 is closed, however, supercharging air cannot enter the cylinder. As will be seen from the position of this closure member shown in'the drawing, this only takes place a short time later. At that moment, however, the closure member 36a in the exhaust pipe 8 is also closed and the cylinder is filled or charged with super-charging air. Later, with the cylinder closed by the piston 4a, compression of the cylinder contents takes place, whereupon there' occurs combustion of the fuel introduced Expansion of the burnt gases follows later, whereupon the exhaust, scavenging and supercharging processes follow each other again in succession. The ports 13a and 15a may be arranged offset in the longitudinal direction of the cylinder, as may be seen from Figure 4. Thereby the passage of the piston rings over the openings or ports is facilitated.

In Figure 5, 2', 2" are the outer parts placed around the inset cylinder 2. 4b is the lower piston and 4 the upper piston. The piston 41: is reciprocated up and down by the crankshaft 25 by means of the piston rod 4 and the connecting rod 4". The piston 4 on the contrary, is reciprocatedup and down by the cross-head 4 the connecting rods- 4 ",the cross-head 4 the connecting rod 4 by eccentric 4i rotating on the crankshaft 25. 5 is the exhaust gas turbine which drives the blower 6. The turbine receives its exhaust gases through the duct 8. The gases leave the turbine through the pipe 9. The scavenging air enters the exhaust gas turbo-blower at 10 and leaves the latter through the pipe 11, whereupon it enters the scavenging air receiver 12. Thence it passes to the cylinder space 14 through the ports 13b, of which there are two rows one above the other. 7b are the outlet ports situated in the upper part of the cylinder, likewise in two rows. 15b are the supercharging ports, through which the supercharging air enters the cylinder 14b when the supercharging air closure member 20 releases the passage to the ports 15b. The supercharging device provided is a two-stage centrifugal blower 58, which receives its aspiration air through the pipe 16 from the scavenging air receiver 12 and the exhaust turbo-blower 6. Said centrifugal blower 58 is multistage and has two rotors 51, 52,21 casing 53 and a driving shaft 56. In the position of the pistons 4b and 4 shown in the drawing, scavenging of the cylinder is taking place. At a later moment, the supercbarging air closure 20 opens and the exhaust gas closure 36b closes and the cylinder is filled with superchargin'g air at a higher pressure than the scavenging air, whereupon compression, combustion, expansion, exhaust and scavenging again follow.

Figure 6 shows a two-stroke engine fitted with crosshead having the working piston 4c. The turbine receives the exhaust gases of the engine through the exhaust ports 7c in the cylinder and the exhaust duct 8, They leave the turbine through the pipe 9 The scavenging air delivered by the blower 6 passes through the duct 11 to the scavenging air receiver 12 whence it passes through the scavenging air ports 13c in the cylinder to the cylinder space 14. Before its admission to the ports 13c the scavenging air is cooled by means of a cooler 21 which receives its cooling medium through the pipes 22' and 23'. Between the exhaust ports 7c and the exhaust gas turbine 5, in this embodiment of the invention, there is no closure member 36 as in the other embodiments shown. Instead, however, the ports 15c for the supercharging air are provided higher up towards the ignition dead center than the exhaust ports 70, .so that upon closure of the latter by the piston and opening of the closure member 20 for the supercharging air, none of the latter can escape to the exhaust turbine through the ports 70. The closure member 20 is therefore only opened approximately when the exhaust ports 7c are covered by the piston, whereby filling of the cylinder with supercharging air commences.

.in this case, the supercharger 78 is in the form of a double-acting piston pump; it has a piston 70 moved by a rod .71 and an arm 72 01f the cross-head 73 of the engine.

16 is the suction duct which obtains its air from the scavenging air distributor 12 and delivers it through the suction valves 74 to the cylinder 75 of the pump, which forces it through the valves 76 to the pressure duct 19 and further to the closure member 20 and the supercharging ports 150 into the cylinder. The working process in the cylinder is shown approximately at the end of the scavenging period. Somewhat later the supercharging process with opened closure member 20 will begin. In this case also, the closure member 20 is driven by a chain 31 and a wheel 32 mounted on the crankshaft 25. 33 is the chain wheel or sprocket for the chain drive 31 which is fixed to an extension of a shaft which rotates the closure member 20.

Figure 7 shows by way of example in connection with the engine of Fig. 4, the pressure 17 as a fun tion of the rotation of a two-stroke engine operating in accordance with the invention. From 0-l05 crank angle, from the upper dead center (OTP) of one of the engines shown in Figures 1, 4 and 6, ignition, combustion and expansion takes place in the cylinder. In the last crank angle, the exhaust ports 7 commence to open and remain open to 255 after the upper dead center, which is represented by the black line a below the pressure diagram. The closure member 36, on the contrary, remains open during the line b with left-hand oblique hatching but close before the end of the opening period of the exhaust ports. The line c, with right-hand downward oblique hatching, represents the opening of the scavenging air ports 13 in the cylinder. The line d, with vertical downward hatching, on the other hand shows the opening of the supercharging ports in the cylinder wall, and the cross-hatched line e shows the period of opening of the closure member 29 for the supercharging air. From the pressure diagram and the control diagrams a--e, it will be seen that shortly before 230 crank angle, the exhaust closure member (36) closes. At this point, or advantageously somewhat later, the scavenging ports 13, line 0, close. The supercharging ports 15, line d, are then still open to about 260 approximately between the time of closing the scavenging air ports 13 (line c) and the closing of the supercharging ports 15 (d), supercharging air flows into the cylinder.

the diagram, so that the approximate duration of the supercharging process can be gathered therefrom.

The present supercharging system of a two-stroke internal combustion engine possesses the following advantages:

(1) Advantages by. the application of low pressure scavenging air:

(a) Small energy expenditure to produce the scavenging air.

(b) Small counter pressure ahead of the turbine to produce the scavenging air. I

(c) As compared to high pressure, low pressure sca enging air does mix with the burnt gases in a lesser degree, because whirling does not take place as would be the case by the use of high pressure scavenging air; in

the latter case, the burnt gases will mix with the scavenging air.

(2) Advantage by the application of high pressure charging air:

Power-output of the motor increases with higher pressure of the charging air, total power-output of the mo tor may be increased considerably.

(3) Advantages'of the design according to the application: 1

(a) The positive displacement compressor driven'by the crank shaft of the engine used as supercharger requires as little power-input as possible, increasing thereby the coeflicient of efficiency of the motor, first because the turbo-blower for the scavenging air is used to supply the suction air of the supercharger and notably because the closing members 20 and 36 for the supercharging and exhaust ports make it possible to supply the motor with accurate quantities of charging air, so that a waste of super-chargingair is efliciently prevented.

(b) Due to the use of the closure members 20 and 36 upon the wall of the cylinders, the effective working space of the cylinders is made greater.

(0) The use of a low pressure turbo-blower and a high pressure supercharging engine respectively independently driven blower has also the advantage that "the known subdivision of the exhaust gas may be dispensed with, providing for all the exhaust gas to be used for the turbo-blower, preventing thereby loss of' energy inherent in the exhaust gas, and improving scavenging of the engine cylinders.

What I claim is:

1. In a two-stroke internal combustion engine of the type having a plurality of working cylinders, each cylinder having exhaust ports, separate ports for the admission of scavenging and of supercharging air situated with the supercharging ports above the scavenging ports, and in which all said ports are formed in the walls of the cylinders, the combination of a turbo-blowerdriven by the exhaust gases of the engine, and of. a mechanically driven blower, the slots of said exhaust ports extending along the axial length of the cylinder wall a distance equal to the axial length of the cylinder accommodating .both the lower scavenging and the upper supercharging air ports, means to operatively connect the output of said turbo-blower to said scavenging ports, and means to connect said mechanically driven blower to said supercharging ports, means to operatively connect .said exhaust ports to the turbine of said turbo-blower, a. first positively operated closure member for the control of the admission of said supercharging air located within said connecting means between the supercharging air admission ports and the mechanically driven blower, a second closure member in said connecting means between the exhaust ports and the turbine of the turbo-blower, said closure members being so positively controlled that in the open position of one closure member the other closure member is fully closed.

2. Two stroke supercharged internal combustion en gine comprising a crank shaft, a plurality of working piston and cylinder means, each cylinder having in its surface at least one exhaust port, atleast one port for the admission" of scavenging air, and at least one port for "the admission of supercharging air, at least one turbine means driven solely by the exhaust gases of the engine, blower means driven by said turbine to supply low pressure scavenging air, means connecting the output of said blower to said scavenging air ports, a supercharger driven by the crank shaft of the engine having an air inlet pipe and an air discharge pipe toprovide supercharging air at a higher pressure than said scavenging air, means connecting the output of said supercharger to said supercharging ports for .the admission of supercharging air, said means connecting said output of said blower :to said scavenging air ports comprlslng a scavenging air receiver formed at least partly around said cylinder means operatively connected to said scavenging air ports, said air inlet pipe of said supercharger being operatively connected to said receiver to supply pre-compressed air from said blower to said superchar er, said ports for the scavenging air being arranged in the wall of said working cylinders beginning axially at the lowermost position of said piston, said supercharging air ports being spaced upwardly from said scavenging air ports, and said exhaust ports being arranged in said working cylinder 'wall .substantially diametrically opposite said scavenging air ports and extending axially beyond said scavenging air ports in the direction towards the uppermost position of said piston, control of said scavenging air ports being by means of said piston, control means for said supercharging air ports and said exhaust ports including rotary closure members, each arranged adjacent its respective port, said closure members for the supercharging air ports .and for the exhaust gas ports being positively operated by means synchronized to the movement of the piston in its cylinder to close the respective ports at predetermined positions of said piston, said means for the output of said supercharger including a safety valve opening into said scavenging air receiver.

3. Two stroke internal combustion engine of claim 1, in which the said supercharging air ports are tangential to the respective cylinders whereby the supercharged air enters the cylinders somewhat tangentially and a rotary movement is imparted to the cylinder contents.

4. The two stroke internal combustion engine of claim 1, in which speed varying drive means for the supercharger connects sa'id crankshaft to said supercharger in order to adjust the quantity and pressure of the air delivered.

5. The two stroke internal combustion engine of claim 1, in which said supercharging air ports are ofiset circumferentially of the cylinders with'respect to said scavenging air ports.

6. The two stroke internal combustion engine of claim .1, comprising on the delivery side of the supercharger a blow-off device and means for delivering its blow-off air to the scavenging air distributor.

7. The two strokeinternal combustion .engine of claim 1, comprising means for cooling the scavenging air delivered by the turbo-blo wer.

8. The two stroke internal combustion engine of claim 1., comprising means for cooling the supercharging air passing from the supercharger to the engine.

9. The two stroke internal combustion engine of claim 1, comprising a common drive for the closure members for the exhaust gases and those for the supercharging air, said drive being driven from the crankshaft of the engine.

10. A two stroke cycle internal combustion engine comprising a crank shaft at least one cylinder having a closed head, a fuel injection means in said head, a piston mounted in said cylinder operating the engine crank shaft for reciprocation between a top dead center adjacent said head and a bottom dead center remote from said head, at least one exhaust port in said cylinder adjacent said bottom dead center, at least one scavenging air port located generally diametrically opposite said exhaust port, at least one supercharging air port in said cylinder wall above said scavenging air port, a turboblower driven by the exhaust gas of said engine, a mechanically driven blower operating from the crank shaft, said turbo-blower operatively connected to said scavenging air port to deliver scavenging air to said cylinder, said mechanically driven blower operatively connected to said supercharging air port to deliver air of higher pressure than the air delivered from said turbo-blower, valve means in said exhaust port and valve means in said supercharging air port, said valves being driven in synchronism with said engine so that said supercharging valve will not open until said exhaust valve is closed and said piston controlled scavenging air ports are being closed by the piston moving from lower dead center to the upper dead center while said valve means for the supercharging air is operatively actuated.

11. The combination of claim 1, wherein said connecting means between the turbo-blower and the scavenging air ports is formed with an air receiver, said scavenging air ports and the inlet to the mechanically driven blower adapted to open into said receiver and to be fed by the air from the turbo-blower.

12. The combination of claim 1, in which a safety valve is provided connecting the discharge of said mechanically driven blower to said air receiver.

13. The combination of claim 1, in which the supercharging air ports are offset circumferentially of the cylinders with respect to the scavenging air ports to reduce wear on the piston rings.

14. The combination of claim 1, including a speed varying drivemeans for the mechanically driven supercharger to provide for the adjustment of the quantity of supercharging air at various operating conditions of the engine.

References Cited in the file of this patent UNITED STATES PATENTS 1,612,143 Moss Dec. 28, 1926 2,051,436 Curtiss Aug. 18, 1936 2,068,878 Suczek Jan. 26, 1937 2,113,979 Bokemiiller Apr. 12, 1938 2,149,982 Rotter Mar. 7, 1939 2,176,021 Grutzner Oct. 10, 1939 2,189,106 Garve et al Feb. 6, 1940 2,197,179 Hershey Apr. 16, 1940 2,305,810 Miiller Dec. 22, 1942 2,766,744 Steiger Oct. 16, 1956 FOREIGN PATENTS 354,242 Great Britain July 30, 1931 488,396 Great Britain July 6, 1938 

